Chinese state-owned oil companies are engaging in ferocious bidding wars with western energy companies as they go after access to the same oil and gas fields, particularly in Africa. The pursuit of "energy independence" has become a bipartisan dream in the US, leading to a big increase in the production of biofuels made from grain which, perversely, has helped to tighten food prices. Middle Eastern investors, in particular the Saudis and the Gulf Arabs, have been leasing huge tracts of land in Africa, in an effort to grow food that is reserved for their own nations. In Europe, supporters of the protectionist Common Agricultural Policy are freshly emboldened.

This new global paranoia about food and energy security is driven by four factors: economics, demography, the environment and geopolitics.

Rapid economic growth in Asia has increased demand for food and energy and helped create destabilising spikes in prices. China's demand for oil has more than doubled over the past decade. Just before the global financial crisis, prices of food and oil were surging, leading some big food producers to restrict exports. Hillary Clinton, the US secretary of state, claimed recently that there had been food riots in more than 60 countries over the last two years.

Today's food and energy scares are sharpened when governments examine demographic and climate trends. The United Nations has estimated that the world's population could exceed 9bn by 2050, compared with about 6.6bn now. This, it says, could necessitate an increase in food production of about 70 per cent from current levels.

Environmental worries add to the paranoia. Even if it now turns out that the Himalayan glaciers will be with us rather longer than the UN climate panel foresaw, politicians such as Britain's Mr Benn regularly cite the threat that climate change will devastate some of the world's most important agricultural land.

Finally, there are the geopolitical concerns. Worrying about sea lanes in the age of the internet sounds anachronistic. But the globalised trading system still relies on moving huge amounts of food and energy around the world by ship - and there are at least three choke-points that look vulnerable to disruption. The one that is getting all the attention at the moment is the Gulf of Aden, just south of the Suez canal, where a large multinational flotilla is fighting the threat from Somali pirates. The Strait of Hormuz, through which most Gulf oil needs to pass, could easily be blocked in the event of a conflict with Iran. Meanwhile, the Chinese government has fretted publicly about its "Malacca dilemma" - the fact that most of China's imported oil from the Middle East has to pass through the Malacca strait, a narrow waterway between Indonesia and Malaysia. China is uncomfortably aware that it is ultimately reliant on the American navy to keep these vital sea lanes open - a fact that may be driving the Chinese effort to build up its own navy.

David Fuller's view Ever since the secular bull market in commodities became apparent in 2002-2003, Fullermoney has expressed concern over the inevitable competition for essential resources which are finite in supply, occasionally scarce, and often costly to produce. These concerns abated during the dramatic economic meltdown of 2008 but have begun to return with economic recovery.

Needless to say, when it comes to hoarding, countries with big current account surpluses are in a much stronger position than debtor nations.

We are right to be concerned about future supplies, not least regarding 'rare earths' frequently mentioned on this site which are increasingly required for many cutting-edge technologies.

Regarding the United Nations estimate that the world's population could exceed 9bn by 2050, Fullermoney remains sceptical of all very long-term forecasts as these are based on little more than trend extrapolations. Secular trends can persist for a long time, but not in perpetuity.

I can think of two reasons - one nasty and one nice - why the global population is more likely to peak at around 7bn and quite possibly decline. 1) A larger population proves unsustainable so more people die before reaching breeding age and/or the stresses produce more conflicts which cull the global population. 2) As more people and particularly women become educated, and as more couples achieve material wealth, they often choose to raise fewer children as we have seen in most developed nations.

I am rooting for number 2 above, and although I do not expect to be around in 2050, good luck to those who live that long.